/Engine/Plugins/Developer/Concert/ConcertMain/Source/Concert/Public/ConcertMessages.h
[USTRUCT](Programming/UnrealArchitecture/Reference/Structs)() struct FConcertSession_CustomResponse : public [FConcertResponseData](API\Plugins\ConcertTransport\FConcertResponseData)
FConcertSession...
SerializedPayload
The serialized payload that we're hosting.